Li Hongsen, Han Boao, Wang Rongyi, Li Wentao, Zhang Wentao, Fu Xuefeng, Fang Huayi, Ma Fuqiu, Wang Zikuan, Zhang Jiajing
School of Pharmacy, Binzhou Medical University, Yantai, 264003, China.
Beijing National Laboratory for Molecular Sciences, State Key Lab of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
Nat Commun. 2024 Sep 4;15(1):7724. doi: 10.1038/s41467-024-50253-9.
Unimolecular reduction and bimolecular reductive coupling of carbon monoxide (CO) represent important ways to synthesize organic feedstocks. Reductive activation of CO through open-shell pathways, though rare, can help overcome the barriers of many traditional organometallic elementary reactions that are hard to achieve. Herein we successfully achieve the unimolecular reduction of CO to (TPP)RhCHOSiRRR (TPP = 5,10,15,20-tetraphenylporphyrin), and the release of products CHOSiRRR, TEMPO-CHOSiRRR and BrCHOSiRRR in near-quantitative yield under visible light (420-780 nm), which involves radical formation from Rh-C bond homolysis. Bimolecular CO reductive coupling products, (TPP)RhCOCHOSiRRR, are then obtained via a radical mechanism. Subsequent treatment with n-propylamine, BrCCl or TEMPO under thermal or photochemical conditions afford small-molecule bimolecular reductive coupling products. To the best of our knowledge, homogeneous systems which reductively couple CO under photochemical conditions have not been reported before. Here, the use of an open-shell transition metal complex, that delivers more than one kind of small-molecule CO reductive coupling products bearing different functional groups, provides opportunities for useful CO reductive transformations.
一氧化碳（CO）的单分子还原和双分子还原偶联是合成有机原料的重要方法。通过开壳途径对CO进行还原活化虽然罕见，但有助于克服许多难以实现的传统有机金属基元反应的障碍。在此，我们成功实现了CO单分子还原为（TPP）RhCHOSiRRR（TPP = 5,10,15,20-四苯基卟啉），并在可见光（420 - 780 nm）下以近定量产率释放产物CHOSiRRR、TEMPO-CHOSiRRR和BrCHOSiRRR，这涉及Rh-C键均裂形成自由基。然后通过自由基机制获得双分子CO还原偶联产物（TPP）RhCOCHOSiRRR。随后在热或光化学条件下用正丙胺、BrCCl或TEMPO处理，得到小分子双分子还原偶联产物。据我们所知，此前尚未报道过在光化学条件下对CO进行还原偶联的均相体系。在此，使用一种开壳过渡金属配合物，可提供多种带有不同官能团的小分子CO还原偶联产物，为有用的CO还原转化提供了机会。
